1. Field of the Invention
The invention relates to glassy metal alloys, and in particular, to glassy hafnium-beryllium alloys.
2. Description of the Prior Art
Glassy metal alloys in wire form have been disclosed by H. S. Chen et al. U.S. Pat. No. 3,856,513, issued Dec. 24, 1974. The glassy metal alloys have the formula T.sub.i X.sub.j, where T is at least one transition metal element and X is at least one metalloid selected from the group consisting of aluminum, antimony, beryllium, boron, germanium, carbon, indium, phosphorus, silicon and tin, and where "i" ranges from about 70 to 87 atom percent and "j" ranges from about 13 to 30 atom percent. As is now well-known, such glassy materials evidence no substantial long-range order. In distinguishing a glassy substance from a crystalline substance, X-ray diffraction measurements are generally suitably employed. Additionally, transmission electron microscopy and electron diffraction can be used to distinguish between glassy and the crystalline state.
A glassy substance produces an X-ray diffraction pattern in which intensity varies slowly with diffraction angle. Such a profile is qualitatively similar to the diffraction profile of a liquid or ordinary window glass. On the other hand, a crystalline material produces a diffraction profile in which intensity varies rapidly with diffraction angle.
These glassy materials exist in a metastable state. Upon heating to a sufficiently high temperature, they crystallize with evolution of a heat of crystallization, and the X-ray diffraction profile changes from one having glassy characteristics to one having crystalline characteristics.
It is possible to produce a metal which is totally glassy or which comprises a two-phase mixture of the glassy and crystalline states. The term "glassy metal" as employed herein refers to a metal which is primarily glassy, but which may have some fraction of the material present as included crystallites. However, since an increasing degree of glassiness results in increasing degree of ductility, it is preferred that the glassy alloy be substantially glassy.
In nuclear reactor technology, hafnium often finds use as control rods because of its high neutron absorption properties and corrosion resistance in hot water. In the fabrication of control rods and the like, hafnium parts are often joined, such as by brazing, to Zircaloy-type and other zirconium-base parts and to other hafnium parts. However, the material used in joining, or brazing, hafnium to zirconium-based parts or hafnium to hafnium often fails due to its poor corrosion resistance or dimensional instability.